Run Microtasks before dispatching onload

Source/core/dom/Document.cpp

Index: Source/core/dom/Document.cpp
diff --git a/Source/core/dom/Document.cpp b/Source/core/dom/Document.cpp
index b92a8112c0063ca79affb5a4686305a1ec804699..d3967a4567c62c1bfd4b06c41c6f65b674913af8 100644
--- a/Source/core/dom/Document.cpp
+++ b/Source/core/dom/Document.cpp
@@ -77,6 +77,7 @@
 #include "core/dom/ExceptionCode.h"
 #include "core/dom/ExecutionContextTask.h"
 #include "core/dom/MainThreadTaskRunner.h"
+#include "core/dom/Microtask.h"
 #include "core/dom/MutationObserver.h"
 #include "core/dom/NodeChildRemovalTracker.h"
 #include "core/dom/NodeFilter.h"
@@ -4616,12 +4617,25 @@ void Document::finishedParsing()
     ASSERT(!scriptableDocumentParser() || !m_parser->isParsing());
     ASSERT(!scriptableDocumentParser() || m_readyState != Loading);
     setParsingState(InDOMContentLoaded);
+
+    // FIXME: DOMContentLoaded should be dispatched in a queued task,

[dominicc (has gone to gerrit), 2015/01/05 07:29:39]

I think a good FIXME does three things:

1. Keeps it short.
2. Explains what needs to be fixed.
3. Explains when the FIXME can be addressed.

I think you don't need the comment here, because it's not a FIXME as much as an
actual bug, so you could comment on Issue 425790 directly. The spec links are
probably useful in the bug thread?

Below I think you want something like:

// Ensure Custom Element callbacks are drained before DOMContentLoaded.
// FIXME: Remove this ad-hoc checkpoint when DOMContentLoaded is dispatched in a
queued task, which will do a checkpoint anyway. (Issue 425790)

[kouhei (in TOK), 2015/01/06 01:37:05]

Done.

+    // but we are dispatching this synchronously at the moment.
+    // Spec: Section 12.2.6 "The end" step 4 and 5:
+    // https://html.spec.whatwg.org/multipage/syntax.html#the-end
+    // See https://crbug.com/425790
     if (!m_documentTiming.domContentLoadedEventStart)
         m_documentTiming.domContentLoadedEventStart = monotonicallyIncreasingTime();
     dispatchEvent(Event::createBubble(EventTypeNames::DOMContentLoaded));
     if (!m_documentTiming.domContentLoadedEventEnd)
         m_documentTiming.domContentLoadedEventEnd = monotonicallyIncreasingTime();
     setParsingState(FinishedParsing);
+    // Perform microtask checkpoint here as a partial fix to make this closer to spec.
+    // FIXME: This should be removed once the above dispatchEvent(DOMContentLoaded) is done asynchronously.
+    // Spec: Section 12.2.6 "Spin the event loop" step 5 says we should spin the event loop here:
+    // https://html.spec.whatwg.org/multipage/syntax.html#the-end
+    // Spinning the event loop includes performing a microtask checkpoint:
+    // https://html.spec.whatwg.org/multipage/webappapis.html#spin-the-event-loop
+    Microtask::performCheckpoint();
 
     // The loader's finishedParsing() method may invoke script that causes this object to
     // be dereferenced (when this document is in an iframe and the onload causes the iframe's src to change).